The present work is based on the available statistics for ca. 4,000 valid mineral species. The United States of America, Russia and Germany produced the largest numbers of species (about 640, 570, and 250, respectively). Between 1775 and 1956, the frequency of discoveries per annum remained at almost the same level, i.e. 10-20 minerals annually, This number was not affected significantly by developments in instrumental methods, and even the advent of X-ray diffractometry did not change it. The breakthrough of 1956-1959 coincided with the institution of CNMMN under the auspices of All-Union Mineralogical Society (USSR) (in 1955) and then International Mineralogical Association (in 1959). Since that time, the frequency of mineral discoveries has been at a level of 30-50 species per year. The number of minerals peaked in 1990-1984, and also contemporaneously with the approval of amphibole-group nomenclature by IMA. First minerals, discovered with the aid of electron-microprobe analysis, appeared in 1962-1963, but the proportion of such minerals among newly approved species began to dominate only in 1974. The greatest number of discoveries has been made by HAIDINGER (early 1800's), DUNN (since the late 1970-es) and KHOMYAKOV (since the early 1960-es). Statistics for individual countries, authors and time periods are presented. The paper also addresses the following issues: (I) structural varieties of minerals and their significance; (II) uncertainties in mineral formulae; (III) validity of minerals whose compositions plot near the 50% boundary; and (IV) significance of isomorphic substitutions for the correct use of the 50 % rule.
